Question

A recessive mutation is?

• A. Not expressed
• B. Rarely expressed
• C. Expressed only in homozygous and hemizygous states
• D. Expressed only in heterozygous state

Answer 1

The correct option is C Expressed only in homozygous and hemizygous states

• Homozygous is a word that refers to a particular gene that has identical alleles on both homologous chromosomes. It is referred to by two capital letters (XX) for a dominant trait, and two lowercase letters (xx) for a recessive trait.
• Hemizygous: Having only a single copy of a gene instead of the customary two copies. All the genes on the single X chromosome in the male are 'hemizygous.

• For a recessive mutation to express itself, the mutated copies must be present on both the chromosomes. For example, if it is X-linked recessive, then the female should have homozygous condition whereas male should have a hemizygous condition.

So, the correct answer is 'Expressed only in homozygous and hemizygous states'.